Searchers located a twin-engine mail plane en route from Billings, Mont., to Salt Lake City that crashed sometime Friday in mountainous terrain 12 miles northeast of Soda Springs, an official said.

A ground crew confirmed Saturday afternoon there were two dead at the site, but their identities were not available, said John Maakestad, assistant safety information officer for the Idaho State Division of Aeronautics.The plane left Billings at 8:30 p.m. Friday and last established contact with Salt Lake City International Airport at 9:20 p.m. Friday, disappearing from radar screens shortly thereafter, Maakestad said.

"We have no idea why the airplane disappeared from the Salt Lake (Federal Aviation Administration) center," he said, adding there were no indications the plane encountered severe weather conditions or suffered mechanical difficulties.

Idaho Civil Air Patrol searchers located the downed craft from the air about 1 p.m. Saturday, Maakestad said. Ground crews were unable to reach the site for some time because the plane had crashed in severe terrain.

The AC-68, owned by Corporate Air of Billings, was carrying mail to Salt Lake City when it crashed into mountainous terrain, strewing letters across a wide area, Maakestad said.

Caribou County Sheriff's officials at the crash site had not determined if there were more than two fatalities, Maakestad said.